Synchronization method



Dec. 31, 1940. K. 'SCHLESINGER' 2227,4107

SYNCHRONIZATION METHOD Filed July 23, 1935 2 Sheets-Sheet 1' Jnren/e/r mm W Dec. 31, 1940. K. SCHLESINGER 2 1 V SYNCHRONIZATION METHOD Filed July 25, 1936 2 Sheets-Sheet 2 mg Q/W Patented Dec. 31, 1940 PATENT OFFICE.

SYNCHRONIZATION ME'rnon Kurt Schlesinger, Berlin, Germany, assignor. by

mesne assignments, to Loewe Radio, Inc a corporation of New York Application July 2c, 1936, Serial No. 92,152

In Germany July 30, 1935 2 Claims. (01. its-69.5)

The present invention relates to the generation of synchronizing impulses in the transmitterof television systems in which the reception is performed by means of cathode ray tubes. Two

kinds of synchronizing signals are wanted, line and frame change signals, and it is well known to generate it in the transmitter by two separate light sirens.

.One object of my invention is a method of generating both groups of signals of higher frequency, the line signals (or in certain cases a multiple of it) and the frame signals by means of only one light siren.

Another object of my invention is to amplifying both groupsof signals by means of the same amplifier tuned to the higher frequency.

Another object of this invention is to separate the lower frequency from the higher frequency used as a carrier by means of a rectifier.

The novel features which I believe to be characteristic for my' invention are set forth with particularity in the appended claims. My invention, however, both as to its organization of operation together with further objects and advantages thereof may 'be best understood by reference to the following description taken in connection with the accompanying drawings, in which Fig. 1 shows an embodiment of a light siren. In Fig. 2 the effect of the light siren is explained,

and

Fig. 3 shows a mechanical and electrical arrangeme'nt according to the invention.

The light siren consists, e. g., of a rim of radial slots 2 (Fig. 1) in the scanning disc I, of which one or more correspond to a scanning-aperture. On the front side of the disc there is projected a sharply defined light image, for example a circle 3, the diameter of which is equal to the spacing 40 between the slots 2. Upon scanning the circle 3 by the slots 2 a practically sinusoidal oscillation is obtained by means of a photo-cell arrangement behind the disc i in a well known manner.- The frequency of these oscillations thus produced is 45 the above mentioned higher frequency."

According tothe invention, the lower frequency (frame frequency) is produced as a modulation of the higher frequency in the followin way:

At a certain place 5 of the rim 4 or more adjacent slots are wholly or partially (as drawn) obturated. In Fig. 2 the oscillations produced by the regular slots 2 are marked with 8. Corresponding to the partially obturated slots 5 the amplitudes 5a are reduced. By rectification of the wave 6 negative impulses 6b are obtained, the frequency of which is equal to the number of revolutions of disc I,. i. e., the lower frequency. I It is understood that this way the higher frequency is used as a carrier. of the lower frequency so that both may be amplified in the same amplifier tuned to the frequency of 6, of course before rectification. I

In certain cases (interlaced line'method), the lower frequency is wanted to be a sub-multiple of the scanning'disc frequency, so that it is impossible to obtain thelower frequency by closing someof the slots. A method of obturation to be used in this case will be described on hand of Fig. 3.

In Fig. 3 there is again shown the disc I, in I and is connected with a highly selective multicircuit tone amplifier l3, which is tuned to-the basic frequency generated by the slots. Thus the higher or line frequency is to be tapped between 22 andearth.

Between light source 1-H) and photo-cell [2 there rotates a shading arm l5, which is driven by asynchronous motor 14 and periodically inamounts, therefore, to several line periods. (See Fig. 2.) The frequency of interruptions (lower frequency) may be equal to or be a multiple or submultiple of'the period of revolution of the disc l.

According to the invention there is connected to the output of the photo-amplifier I3. a rectifier consisting preferably of a diode I6, a blocking condenser i1 and a leak-resistance IS. The impulses 6b of Fig. 2 of the lower frequency" obtained by the rectifier are positive or negative, according to the polarization of i5, and are, preferably by means of a filter 23, 24 and a series resistance 25 conducted to the control grid of an amplifier tube 20. It has been found in practice, that a single screening grid tube is quite sufiicient to generate at its anode frame change impulses, the amplitude of which is Just as great 'terrupts the light. The interruption has the duration of'the designed image-change signal, and

as the amplitude of the line-tone oscillation,

- variation in theworking conditions of the con-.

trol grid circuit, which operates with fixed biases. The method may naturally also operate with a periodic brightening of the illumination in-=- stead of a periodic obturation, as described. In this case all polarities are reversed. In Fig. l. and Fig. 2 the closed or nearly closed slots are replaced by wider ones, in Fig. 3.instead of the shading member a window or radial slot is employed and at to, and 6b the amplitudes become higher instead of smaller.

The method may be employed with all the better result the higher the carrier frequency -may be. In the case of a slotted disc with a multiple slot frequency as compared with the line frequency and subsequent reduction to the line frequency the amplifier i3 is traversed by a carrier wave of particularly high frequency, and

it is possible therewith to produce special line and image change signals. In the case of a 180- line image the normal line-frequency, for example, amounts to 4,500, and in the method making use of interlaced lines and a double spiral disc the line frequency amounts to approximately 9,000 and in the methodof employing 4 spirals to 18,000 periods. The duration of the imagechange signal amounts in comparison therewith to approximately $5 sec. .and may accordingly be 'taken with an" adequate efliciency from the carrier oscillation even in thecase of .very selective amplifiers. I

It may be specifically pointed out that in the 'above there have merely been described particular embodiments of the general idea according to the invention, and that the stated measures may be employed and claimed both in combination as well as singly.

I claim:

1. A system for generating relatively high frequency line synchronizing impulses and relatively low frequency frame synchronizing impulses 'for television image transmission comprising a disc having a plurality of radial slits of a predetermined length located near the periphery of the disc and uniformly spaced around the disc,-

tensity by the slits lying within the said relatively small sector of the disc, and means to demodulate the modulated voltage variations to produce voltage variations of the said relatively low frequency.

2. a system for generating relatively high frequency line synchronizing impulses and relative ly low frequency frame synchronizing impulses for television transmission comprising a disc having a plurality of apertures of a predetermined size located near the periphery oi the disc and uniformly spaced around the disc, the apertures lying within a relatively small sector of the disc having a size difierent from the size of the remaining apertures, means to rotate the disc, means to project a beam of radiant energy onto the disc in the region of the apertures, the circumferential dimension of the beam of radiant energy being less than the spacing between the apertures, a radiant energy responsive element positioned to receive the radiant energy projected through the apertures to produce potential variations of a multiple of line synchronizing impulse frequency, the potential variations being modulated in intensity by the apertures lying within the said relatively small sector of said disc, and means to 'demodulate the modulated voltage variations to produce potential variations of a multiple of frame synchronizing impulse frequency.

KURT SCHLESINGER. 

